I was thinking about swapping to a 18F. They seem to be better for ram and oscillator speed although im already using 20Mhz and you say that is enough.

I understand your explanation about instruction cycles but you lost me a bit with the us explanation.

If i have all these cycles spare then does it matter whether i process the data in the main loop or the interrupt handler? What exactly is an "instruction cycle"? Is it the same as a word? (I mean word asin "Success : 100 words used", not the data type)

How do you know how long it takes to execute each instruction cycle? The datasheet says its 200us but that changes depending on the oscillator.